Waiting for a game?

I'm interested in GMing Pathfinder. Been involved with the game since it came out, and I've been GMing PbP on another site for almost 10 years. Never GMed here, but I have a close friend who is doing so, and doing what seems to be an exemplary job of it.

One thing that might be a sticking point: Do PFS-sanctioned adventures have to use published adventures? I ask because I think that I basically just have some one-shot adventures and one complete AP, but it's probably the worst-reviewed AP that there is. It's Second Darkness. I kinda like it, but the ending needs to be homebrewed pretty extensively. Is that even allowed in PFS?

For PFS play, it must be PFS-sanctioned adventures run as written. This is to maintain a level playing field, since consumables spent on an encounter one GM didn't think was epic enough can throw off WBL for the rest of that character's life. In a home game, that wouldn't be as big a deal, since the GM can adjust treasure as necessary.

Luckily (or unluckily), Second Darkness hasn't yet been sanctioned for PFS at all. For adventure paths and modules, check the Additional Resources for Chronicle Sheets. If they aren't there, it's not PFS-legal.

The adventure has to be sanctioned for PFS, which means yes, it would have to be a published adventure. That said, there are some non-PFS specific modules that are sanctioned for PFS play. Unfortunately the Second Darkness AP is not sanctioned, likely because it is a 3.5 adventure that was created before the PF rules.